A manual transmission has four attributes visible on the exterior: (A) the input shaft that splines into your clutch and takes rotational power from your engine; (B) the output shaft that splines into your transfer case and delivers rotational power rearward; (C) the shift tower (top plate) that houses the shift rails; and (D) the case. The case is where all the gears are carried. Some transmissions, such as this NV-4500, also have a tailhousing for additional gear space.